runtime: fix arm build

TBR=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/140990043

diff --git a/src/pkg/runtime/atomic_arm.c b/src/pkg/runtime/atomic_arm.c
index 5369820c0902120adb0e822afa9d8e5f98861e76..487b128cbbeca7628b131e161f14c0c6e891879b 100644 (file)
--- a/src/pkg/runtime/atomic_arm.c
+++ b/src/pkg/runtime/atomic_arm.c
@@ -58,7 +58,7 @@ runtime·xchgp(void* volatile* addr, void* v)
 void*
 runtime·xchguintptr(void* volatile* addr, void* v)
 {
-       return runtime·xchg((uint32*)addr, (uint32)v);
+       return (void*)runtime·xchg((uint32*)addr, (uint32)v);
 }
 
 #pragma textflag NOSPLIT